THE SIGNAL BOX

BLOCK SYSTEM

BLOCK SYSTEM

9. Alarms and excursions

On this page:
[ Obstruction danger | Without tail lamp | Train divided | Train running away | Stop and examine | Long time in section ]


A range of emergency bell signals existed, with a complex range of necessary responses according to the circumstances. Whilst the actions taken are too complex to warrant detail here, an overview of the use of each bell signal is given.

Obstruction danger

If Bert becomes aware of any obstruction that would endanger a train approaching him from Box A, irrespective of whether at train has been signalled or not, he would send the Obstruction danger signal (6 beats, not preceded by Call attention) to Arthur at Box A and place the block indicator to Train on Line. When the line is again clear, Bert will send the Obstruction removed signal, which is identical to Train out of section (2-1) and replace the block indicator to Normal.

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New "improved" layout at Signal Box "B"

Train passed without tail lamp

As detailed in Chapter 2, Bert carefully checks each train for its tail lamp, to confirm the entire train has left the section. If the tail lamp is not there, it is possible the train has become divided - a not unknown circumstance in the days of loose-coupled (unbraked) freight trains. Should part of an unbraked train roll back on the gradient over catch points, it may be derailed, too. If a Down train passes Box B without a tail lamp, Bert will send Train Passed without tail lamp to both Box A (9 beats on the bell) and Box C (4-5 bell signal), continuing to regard the section from Box A as occupied.

Arthur at Box A will stop the train if he can do so without sudden braking (which has been known to cause a train to become further divided), otherwise he will forward the Train passed without tail lamp signal to the next box for it to be stopped there. Only when the guard of the train has confirmed the train is complete, may Train out of section be sent by Bert for the train concerned.

If a Down freight train passes Bert without tail lamp and side lamps (additional lamps carried on freight trains) Bert must assume the train is divided and act in accordance with the regulations for divided trains, detailed below.

In all the above circumstances, steps are taken to stop and warn drivers of trains on the adjoining line(s).

If a train passes with a tail lamp unlit when it should be burning, but Bert can establish that it is present at the rear of the train, he should send Train passed without tail lamp to Arthur at Box A, but may send Train out of section to Charlie at Box C because he knows the whole train has left the section complete.

Tail lamps were required, at that time, to be lit only during darkness and when passing through certain tunnels listed in the Sectional Appendix.

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Train divided

This bell signal is only used in certain circumstances where, taking into account the gradient of the line, it is likely that two portions of a divided train will both proceed into the section ahead. The purpose of this is to prevent the second portion (that has become detached through, say, a broken coupling) colliding with the leading part of the train.

In our example, let us consider the fact that the Down line from Box C to Box A is downhill all the way. A loose-coupled coal train has passed Charlie with no tail or side lamps, an not even a brake van! He realises the train must have become divided and, despite the fact that the guard has probably screwed his handbrake down as hard as it will go, the second portion may well be running out of control on the steep gradient close behind the front part of the train.

In these circumstances, Charlie does not send Train passed without tail lamp to Bert, but instead sends Train divided (5-5) to indicate that both portions of the train are likely to enter the section.

Bert will do all he can do to avoid a collision. If he had a junction facing that direction, he might consider diverting one portion of the train to the branch line - he must use his judgement on this. If the is no choice but to allow the two portions to continue to Box A, Bert will (if the train has already been accepted) send the 5-5 signal forward to Arthur. Bert will also advise the driver of the circumstances by displaying a green flag waved slowly from side to side as the train approaches.

Even if the section ahead is still occupied, Bert can admit the first portion of the affected train into the section in order to avoid collision or reduce the impact, subject to a number of conditions, including:

If these conditions are met (and any signalman faced with this dilemma needs a quick brain), Bert may clear any signals except his section signal and display a green flag or lamp waved slowly from side to side to inform the driver of the circumstances and authorise him to enter the section ahead. Thus, the fundamental rule of only one train in any block section at a time is allowed to be broken.

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Train or vehicles running away

In any circumstances where a train or vehicles are running away out of control into a block section, other than as described above, the special "Train running away" bell signals must be sent. There are two signals, one for Train running away in right direction (4-5-5), and Train running away in wrong direction (2-5-5). The Call attention does not precede these signals, and in both cases the block indicator must be set to Train on Line.

Situations where these bell signals might be used are:

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Stop and examine train

Apart from all his other responsibilities, Bert is required to watch carefully every train as it passes his box. Should he notice something unusual, such as

he must, after sending Train entering section, send Stop and examine train (7 beats) to the box in advance - Box C in the case of an Up train. Charlie at Box C will do all he can to stop the train concerned. Trains on the adjacent line will generally be stopped, too, as a precaution.

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Train an unusually long time in section

This bell signal is unlikely to concern Bert, because it only applied on multiple running lines. If a train is an unusually long time in section, it may have broken down, maybe miles from the nearest telephone. Worse still, it may be derailed. In these circumstances, trains on the adjacent line(s) must be stopped and their drivers warned.

If there is another line for traffic in the same direction as the "missing" train, and a train has already been accepted on that line, the Train an unusually long time in section signal (6-2) must be sent so that the train can be stopped and cautioned. If no train has been signalled, a telephone conversation will suffice.